Lower Thread Is Lifted Up At The Sewing Start; Uneven Seams; Seam Lifts Up At The Sewing Start - Brother HE-800B Instruction Manual

11. TROUBLESHOOTING
11-4. Uneven seams (2) ...... Lower thread is lifted up at the sewing start
The end of the lower thread protrudes above the seam at the sewing start
Items with a "*" in the "Page" column should only be handled by a qualified technician.
Cause
Lower thread retainer
Lower thread clamp
11-5. Uneven seams (3) ......Seam lifts up at the sewing start
Seam lifts up and does not tighten at the sewing start
Items with a "*" in the "Page" column should only be handled by a qualified technician.
Cause
Upper thread trimmer
Upper thread feeding
81
Check
Lower thread retaining
amount
Lower thread clamp
opening timing
Lower thread clamping
force
Check
Upper thread trimmer
gradual opening timing
Upper thread trimmer
operation
Thread take-up amount
Remedy
Adjust the lower thread retaining amount.
Adjust so that the lower thread clamp plate opens
when the feed mechanism moves 6 - 7 mm.
・If the lower thread clamp and lower thread presser
are bent, replace them.
・Check that the screws are tightened.
Lower thread
clamp
Remedy
Adjust the timing so that the upper thread trimmer
gradually start opening when the feed mechanism
moves about 1.5 - 2.5 mm.
Apply grease to the inclined face of the opening cam.
Loosen the screw to decrease thread take-up amount
so that upper thread does not pull out of trimmer
assembly at the sewing start.
Increase
Decrease
HE-800B
Page
*
4003Q
70*
Screw
*
3999Q
Page
69*
69*
Screw
*
4000Q